Ubuntu is not ready for human beings
I'm a human being and I like Linux including the command line stuff. I use Debian, Ubuntu and OpenSuse on daily basis. I would like to recommend Linux to other human beings. Ubuntu is the most popular choice. However from Edgy Eft to Intrepid Ibex Ubuntu has regularly disappointed me.
1. Updating Ubuntu to a new release is simple, but each time it will break something. This may be true for other operating systems, too, but Ubuntu releases 16 times more often then Microsoft does. No human being wants his most important device broken twice a year.
2. If you don't test it, it doesn't work, right? I can make a long list of packages in each Ubuntu release (all repositories because I don't know or care which packages are in "universe" or somewhere else) which have never been tested by the maintainer. I can usually fix it by editing a conf file, setting file permissions, etc, but it doesn't make a good impression if the default configuration doesn't work.
The points above can be blamed on Ubuntu's release schedule which allows only two month from "feature freeze" to the final release.